Preserva on Assessment

Transcription

1 Preserva on Assessment For Mill Road over Neshaminy Creek BMS # Bucks County PennDOT Engineering District 6 0 Final Report Dec 2017 Prepared by TranSystems for the Pennsylvania Department of Transporta on Environmental Policy and Development Sec on

2 BRIDGE LOCATION LOCATION VICINITY N BRIDGE LOCATION MAP Mill Road (T-381) Over Neshaminy Creek Buckingham and Warwick Townships, PA Source: PA Type 10 Map Bucks County

3 RESOURCE LOCATION QUADRANGLE LOCATION SCALE SOURCE 0ft 2000ft USGS 2013 Buckingham, PA N Mill Road (T-381) Over Neshaminy Creek Buckingham and Warwick Townships, Bucks County, PA

4 PENNSYLVANIA METAL TRUSS BRIDGE PRESERVATION/REHABILITATION ASSESSMENT EVALUATIONS The purpose of this assessment is to provide a benchmark analysis in which to understand rehabilitation options based on existing conditions of the bridge and adjacent areas at the time of the analysis and the observed usage. This assessment is not a Historic Bridge Rehabilitation Analysis, with purpose and need established, and a more in-depth study may be required if the project is to be further developed. The ability of this analysis to determine whether the bridge can be rehabilitated to meet project need is constrained by the fact that actual need is not established for this analysis and that data utilized is based on a field view, file research, and chance interviews with local parties. When actual project need is established, this information will be updated based on current field data. A final determination of whether rehabilitation can meet the project needs and would be considered feasible and prudent under Section 4(f) of the USDOT Act of 1966 will be determined during the NEPA/Section 4(f) process. BMS #: Bridge Key #: 7529 District: 6-0 County: Bucks Township: Buckingham/Warwick Owner: County Maintenance: Bucks County Location Information: East of SR 263 and north of Jamison in Park Bridge Name: Mill Road over Neshaminy Creek Bucks County Bridge No. 127 Type: Through Truss Design: Double Intersection Pratt (pinned) Truss Materials: Wrought Iron Date: 1888 Alter/Rehab: N/A Source: Inspection File Length: 290' Number Spans: 2 Main Span: 140 Deck Width: 15-6 (out-to-out dimension) Bridge Description The skewed, wrought iron, 290 -long, 2-span, pin connected, double intersection Pratt (Whipple) thru truss bridge is supported on rusticated ashlar abutments and a cutwater pier with a concrete toe wall. The bridge deck is 15'-3" wide and comprised of an open steel grid deck supported on rolled floorbeams and stringers. The upper chords and inclined end posts are traditionally composed box sections, and the verticals are laced Mill Road Bridge Assessment Page 1

5 channels. Cast iron chafe guides are used to carry the loop forged eyebars past the verticals. The portal braces have lattice fill, and the upper lateral bracing is composed of laced channels. The original railings as well as any maker plaques have been lost. The present railings are channels welded to the truss lines. Extra floorbeam hangers have been added to the hip panels, and lateral bracing has been welded to the interior panel verticals. NR Eligibility Status: Eligible under Criterion C for technological significance. Historic Preservation Priority: Exceptional (see Protocols for Levels of Priority located at Historic Preservation Priority Justification: This wrought iron bridge is technologically significant as a relatively early and complete example of an uncommon thru truss design. The double intersection design (diagonals extend across two panels instead of the much more common one panel) was used to achieve longer span lengths. This multi-span, bridge is an early example of a double intersection Pratt in the state and the earliest example in District 6, where they are rare. The character-defining features include the truss material, truss form and method of truss member end connection (pin connected, double intersection Pratt [Whipple] thru truss) and the floorbeam connection detail (floorbeams connected below the bottom chord with U-bolt hangers). Decorative elements (portal bracing and cast iron chafe guides used to carry the loop forged eyebars past the verticals) are also significant features. Roadway & Site Information Setting Description: The bridge is located in a wooded setting in a formerly rural area with later single family home houses scattered among the old farmsteads. It is located in Dark Hollow Park that was established by Bucks County in 1989 when plans to construct the Dark Hollow dam and impoundment on the main stem of Neshaminy Creek. The dam was to be part of the Neshaminy Creek stormwater management program to reduce flooding. The park follows the creek banks and its tributaries. The Old York Road stone arch bridge is in the park upstream of this bridge. There is no access to the park at the bridge. Type of Bridge Service: One lane (less than 18'-wide travelway) serving twodirectional traffic. Bridge Roadway Width: 15-3 Approach Travelway Width: 18' Vertical Clearance: 11-3" Functional Classification: Rural Local Mill Road Bridge Assessment Page 2

6 ADT(Date): Present ADT = 0 vpd, as the bridge is currently closed to traffic. The 2010 BSM2 lists an ADT of 50 vpd (0% truck traffic). The source of the BMS traffic count on the bridge is not known. The bridge has been closed to all traffic since September, Since AASHTO guidance on bridge width is founded on the number and types of vehicles that use a bridge, starting with an accurate assessment is critical, especially when the ADT on a rural local road is less than 400 and is projected to remain under 400 for 20 years. When bridges that do not meet current design criteria (functionally obsolete) are located on very low volume local roads and are performing satisfactorily (absence of documented crash history), AASHTO policy affords the opportunities to keep functionally those bridges in service. Shoulders/Sidewalks: None. Observed Crash History: Minor impact damage is present on U9L9 of the right truss in Span 1. The damage appears to have been an isolated incident. Specific crash history data (from local police) was not available for this site, so observed conditions of impact were used to make a determination. Safety Features: Transition guide rail and an appropriate treatment at the bridge ends is needed and none is provided. The railings do not meet current design criteria, and they have the potential to puncture tires and snag vehicles. Proximity of Alternate Routes: There is one nearby alternate route available that is 2.2 miles long, using School Road, SR 263 (York Road), and Sugar Bottom Road. This route does not have any bridges with height or weight restrictions. The actual additional length traveled would be dependent on the ultimate origin and destination of the individual traveler as the local roadway network is fairly well developed to permit sufficient connectivity. Summary Geometric Deficiencies: With a bridge deck roadway width of 15-3 and 11-3 vertical clearance, the bridge is classified as functionally obsolete because it does not meet the 18' definition of a two lane facility. The approach roadways have slightly limited sight distance due to the horizontal curve at the east approach and the vertical curve at the west approach. Performance Summary: When the bridge was open to traffic (restricted to a load of 6 tons), while it did not meet current design requirements, there was no evidence of a significant crash history and therefore it appears that the bridge was operating in a safe manner for those vehicles permitted to use the bridge at that time. Hydraulics: Neshimany Creek flows from west to east and enters on a skew through Span 1, impacts the pier, and exists on a skew. There is secondary flow and overflow under Span 2. The banks range from flat to moderately steep with heavy bank erosion Mill Road Bridge Assessment Page 3

7 along the upstream near left bank. Large flood debris (trees, logs, branches, etc.), soild deposits, and vegetation exist in the dry span (Span 2) overflow channel. There is a large sediment deposit at the far face of the pier. There is an occasional chance of overtopping, as per BMS 2. BMS Condition & Load Sufficiency Condition Code Ratings (2016) Superstructure: 1 Imminent Failure Substructure: 5 Fair Deck: 7 Good Controlling Load Ratings Inventory: 6 T Operating: 8 T Posted: Yes (6 tons before closure) Method: Load factor (floorbeams & stringers) Allowable Stress (truss) LOAD FACTOR METHOD (unless noted otherwise) STRUCTURAL MEMBERS H20 (20 Tons) HS20 (36 Tons) ML80 (37.74 Tons) TK527 (45 Tons) STRINGERS (inv.) STRINGERS (opr.) FLOORBEAM (inv.) FLOORBEAM (opr.) (1)(2) TRUSSES U5L5 (inv.) (1)(2) TRUSSES U5L5 (opr.) (1) Controlling Members (in red) (2) Allowable Stress Method The latest analysis is from Truss member U5L5 controls the ratings with a posting of 6 tons at inventory stress levels. All rating numbers are below required levels for the vehicle listed. For truck loading schematics showing the axle loads, see Appendix. The inventory rating level results in a live load which can safely utilize an existing structure for an indefinite period of time. The operating rating level generally describes the maximum permissible live load to which the structure may be subjected. Allowing unlimited numbers of vehicles to use the bridge at operating level may shorten the life of the bridge. Summary Structural Deficiencies The bridge is rated in overall imminent failure condition (1) due to the condition of the superstructure. Based on BMS2 data, confirmed by a cursory field view, the following specific deficiencies were observed. Refer to photographs for additional details. Mill Road Bridge Assessment Page 4

8 Truss Lines The upper and lower chord members exhibit minor to heavy surface rust and pitting. The left side of Span 1 exhibits a missing section of the vertical tension member adjacent to the lower chord at member U1L1. The left side of Span 2 has three locations of 100% section loss of primary vertical members at the lower pin connection The right side of Span 2 has two locations of 100% section loss of primary vertical members at the lower pin connection All pinned connections exhibit moderate to heavy pack rust Many top chord members have sever corrosion, section loss and holes The upper lateral brace at U6 and U7 exhibit areas of 100% section loss on the bottom channel One lower chord member is bent on the left side of Span 1. The inclined end posts have moderate impacted rust. One diagonal is no longer aligned with its guide on the right truss There is moderate pitting of all wrought iron throughout Bearings The encased steel roller bearings at the pier are displaced with the rollers out of the encasement. Floorbeams All of the nine rolled steel I-beams with welded cover plates in the floor system exhibit moderate to heavy surface rust and pitting. The added hangers are intact at all hip panels. The severed floorbeam hanger is not an original design feature but is common for Bucks County alterations to its pin connected thru truss bridges. Stringers The seven rolled steel I-beam stringers exhibit moderate to heavy surface rust and pitting most pronounced on the fascia beams and at the abutments and pier. The stringers are not bearing on the abutment seat at the north abutment. Bracing There is a holed through section at the end lateral bracing on the near truss and a hole in the right upper chord. Substructure The stone masonry substructure units are in fair condition. Both abutments have isolated areas of minor to moderate joint loss and or deterioration. The northwest U- wingwall has been repointed but there is moderate bulging at the end of the wall. The mortar joints at the south wingwalls are heavily vegetated. Portions of the concrete apron around both abutments are visible. The mortar joints of the stone masonry solid wall pier are vegetated and exhibit moderate amounts of deterioration. Several stones are missing from the top of the pier at the upstream nose. There is a local scour Mill Road Bridge Assessment Page 5

9 condition along the near face and downstream end of the pier with the footing exposed up to 3 feet high with no undermining. Rehabilitation & Preservation Considerations Benchmark for Assessing Rehabilitation The existing bridge has an exceptional historic preservation priority and is located on a very low volume local road with an extremely low reported volume of traffic. There is a nearby alternate route that is detailed on Page 3 that provides access to the adjacent areas of the bridge. It needs to be determined if a bridge is necessary at this crossing and if making the needed structural repairs to make it satisfactory could be undertaken. The bridge has structural deficiencies related to deterioration of the trusses, floor system and the coating system. There are conventional treatments to correct the deficiencies. Specific Options to Address Existing Conditions and AASHTO Criteria The options considered strive to address the documented structural deficiencies associated with the physical condition of the bridge, such as failing paint and related corrosion. Traditional treatments for improving load carrying capacity based on the capacity of the trusses are considered. This analysis is based on considering options that make the bridge structurally satisfactory while preserving what makes it historic. Options for addressing the deficiencies are divided into four categories (1) maintenance; (2) rehabilitation without adverse effect; (3) the option of building on a new location without using the old bridge and (4) other reasonable options. Maintenance The bridge has deteriorated beyond the point where the structural deficiencies can be addressed by routine maintenance. However, if the bridge were to be repaired and repainted, there are conventional and cost effective treatments that could be performed on a routine basis in order to significantly reduce life cycle costs, like cleaning the bridge to maximize the life of the coating system. Rehabilitation without Adverse Effect Section 106 of the National Historic Preservation Act of 1966 (NHPA) requires federal agencies to take into account the effects of their proposed improvement on historic properties. An adverse effect on an historic resource occurs when the proposed improvement alters the character defining features that qualify the property for inclusion in the National Register. Adverse effects can be avoided by rehabilitating the structure to the Secretary of Interior s Standards for Rehabilitation. This could be accomplished by implementing the following rehabilitation program. Rehabilitation of the bridge would include conventional treatments that would not alter the characteristics that make the bridge historically significant. Structural deficiencies can be addressed by replacing deteriorated sections or the entire members of the truss Mill Road Bridge Assessment Page 6

10 and flooring system with an in-kind repair or total replacement. A No Adverse Effect is likely as long as the existing end connection details are utilized (pinned truss members and the floorbeam connection detail). Rivets do not need to be utilized for built-up members. Truss strengthening to achieve a higher load capacity can also be achieved without adverse effects by in-kind replacement with a higher strength material or providing a secondary support system (i.e. post-tensioning or adding supplemental members). Truss expansion bearings would be replaced with neoprene or polytetrafluoroethylene (PTFE, better known as Teflon ) bearings while the fixed bearings would be cleaned and repainted. The substructure units could be rehabilitated and this will not adversely affect the historic significance and cultural value of the bridge as they are not considered a character defining feature of the bridge. Appropriate placement of safety features to protect motorists and the truss lines is also permissible. The existing bridge railings are not original and could be removed and new railings installed which are not attached to the trusses. The following budgetary cost estimate has been developed (utilizing unit costs generated from previous truss rehabilitation projects and modified to reflect specific site constrains/conditions) to provide a rehabilitated structure that makes the bridge satisfactory for this site and meets a 15 ton minimum capacity. This value is the generally accepted minimum load carrying capacity for rehabilitated structures and represents the anticipated weights for a school bus, oil delivery truck, and small emergency service vehicle. Based on a review of the available structural analysis, it appears that a rehabilitation that results in a 20 ton weight limit would be possible without adverse effect; however, 20 additional truss members would require strengthening. If additional carrying capacity is determined to be required when a purpose and need is developed for the project, additional analysis would be needed. This would be addressed by means of additional analysis during the NEPA process. Mill Road Bridge Assessment Page 7

11 Cost Model - Rehabilitation Program for 15 Ton Capacity Remove Portion of Existing Bridge L.S. $25,000 Temporary Superstructure Support L.S. $100,000 Pointing 480 $30/SF $14,400 Reset Loose Stones 25 $150/SF $3,750 Truss Repairs/Strengthening $10,000 $240,000 Truss Bearings $10,000 $20,000 Clean & Paint Superstructure L.S. $350,000 Floorbeam Repairs 18 $7,500/EA $135,000 New Stringers 5 x 34 x 30# = 5,100 LB x $3.50 $17,850 Bridge Railing 246 x $75 $18,450 Approach Guiderail 300 x $50 $15,000 Subtotal: $939,450 20% $187,890 TOTAL: $1,127,340 Considering a 25 year life-cycle analysis that includes a 3% inflation rate and yearly flushing of the truss and bridge seats and spot cleaning and painting, the following costs could be added to this cost model. The cost does not include engineering, mobilization, maintenance and protection of traffic, erosion control measures, etc. Flushing Truss/Bearing Area $1,000/YR 25 ($1,550 ave.) $38,750 Spot Cleaning & Painting 15 years $38,950 TOTAL: $77,700 The cost model yields a total rehabilitation program in present dollars equal to $1,210,000. The cost for a bridge replacement is estimated to be approximately $1,625,000 based on similar statewide projects. The cost does not include engineering, mobilization, maintenance and protection of traffic, erosion control measures, etc. Other Reasonable Options For Reuse This is a very low volume local crossing, and there is an alternate route to access properties on either side of the bridge. Although meeting any likely need, the cost for building a new bridge on a new alignment in close proximity to the existing structure while leaving this historic bridge in place is essentially the same as replacement. Ownership and maintenance of the existing bridge is left undetermined, which might not be conducive to long-term preservation. If it is determined that the actual need does not require a crossing at this location, then removal, relocation, and rehabilitation of the existing structure to the Secretary of Interior s Standards for Rehabilitation is an option that could also result in a No Adverse Effect. Likewise, if construction of a new bridge is required at the crossing based on project, then the removal, relocation, and rehabilitation of the existing structure to the Mill Road Bridge Assessment Page 8

12 Secretary of Interior s Standards for Rehabilitation is also an option that could result in a No Adverse Effect. That work would still require that the truss deficiencies be addressed and the bridge cleaned and painted. Due to the length of the span, it is anticipated that this would involve dismantling, rehabilitating, conserving and then relocating the truss for reuse. Summary of Rehabilitation Options Ultimately, the investment into a rehabilitation of a historic bridge works best when there is a long-term potential for preservation. Because of that goal, there is a hierarchy of rehabilitation options. Highest is the rehabilitation of the existing bridge at the current location that continues to meet transportation need at that crossing. Below that is a relocation and rehabilitation of the bridge to another crossing or rehabilitation of the bridge on existing location for a use other than the transportation need. The least preferred option is dismantling and storage of the historic bridge for a future use. This provides no assurance that the bridge will ever be rehabilitated and re-used, and would result in a finding of adverse effect. Based on the observed conditions and usage prior to closure, the Mill Road Bridge could be rehabilitated to carry 15 tons without altering its character defining features and could still be eligible for the National Register. The cost of the rehabilitation would be less than the cost of a new bridge. There are definite challenges to moving forward with rehabilitation due to the work that must be done to address deterioration of the truss members, but rehabilitation appears to be a cost effective option. With conventional treatments for repairing or replacing these elements on the trusses and cleaning and painting the trusses with a properly done coating system, it is likely that the bridge would last a minimum of 25 years with routine maintenance. If construction of a new bridge is required at the crossing based on project needs or if the actual need does not require a crossing at this location, removal, relocation, and rehabilitation of the bridge would likely result in a No Adverse Effect finding and provide utility of the structure in another use. That use could be in a transportation purpose or in a non-vehicular use. Mill Road Bridge Assessment Page 9

13 SUGAR BOTTOM ROAD T-340 MILL ROAD T FLOW NESHAMINY CREEK 9 1 LEGEND X PHOTO NUMBER AND DIRECTION NTS TITLE MILL ROAD

14 Photo 1 South Elevation Photo 2 Upper Bracing Mill Road Bridge Assessment Photo Page 1

15 Photo 3 Through Shot Looking East Photo 4 Impacted Rust at End Post Mill Road Bridge Assessment Photo Page 2

16 Photo 5 Top Chord with Impacted Rust Photo 6 East Approach Looking East from Bridge Mill Road Bridge Assessment Photo Page 3

17 Photo 7 East Approach Looking East Photo 8 Through Shot of Bridge Looking East From West Approach Mill Road Bridge Assessment Photo Page 4

18 Photo 9 View Looking North at Pier Photo 10 South Elevation at West End Mill Road Bridge Assessment Photo Page 5

19 Photo 11 Typical View of Bridge Underside Photo 12 Typical Lower Panel Point Mill Road Bridge Assessment Photo Page 6

20 Photo 13 Lower Panel Point Detail Photo 14 Typical Masonry Substructure Mill Road Bridge Assessment Photo Page 7

21 Photo 15 Bridge Seat with Vegetation Growth Photo 16 Typical Transition of Bridge Railing To Approach Barrier Mill Road Bridge Assessment Photo Page 8

22 Photo 17 Truss Diagonal to Vertical Detail Photo 18 Typical Rust at Bottom Chord Mill Road Bridge Assessment Photo Page 9

23 Photo 19 Upper Chord Detail Photo 20 Bottom Chord At Near Left Bowed Mill Road Bridge Assessment Photo Page 10

24 Photo 21 Typical Vertical Condition Photo 22 Broken Hanger at Near Left Mill Road Bridge Assessment Photo Page 11

25 Photo 23 Section Loss to Upper Lateral Bracing Photo 24 Typical Bottom Chord Panel Point Mill Road Bridge Assessment Photo Page 12

26 Photo 25 Wingwall Deterioration Photo 26 Typical Abutment Header Mill Road Bridge Assessment Photo Page 13

27 Photo 27 East Wingwall Mill Road Bridge Assessment Photo Page 14

28 Appendix Truck Loading Information

29 The figures below show common truck axle loadings used for analysis of bridges in the state of Pennsylvania. Note the following: One KIP = 1,000 pounds 2,000 pounds = 1 Ton One wheel load = Axle load divided by two The following sheets show the approximate weights of common vehicles.

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